1Technical Field
The present invention relates in general to a mass memory optical disk data storage system for use in a data processing system and, more particularly, to a method of formatting embossed header patterns on the optical disk. More particularly still, the present invention relates to providing embossed header format on bi-level optical media to reduce adjacent track crosstalk during a header play back operation of the optical disk.
2. Description of the Related Art
One type of optical disk drives, such as those using either ISO standard 130 mm rewritable or write once, read many (CD-WORM) optical disks, uses a push/pull tracking method. These optical disk types have guide grooves or so-called pre-grooves formed previously along with the formation of sector header information on the disk. These grooves are irradiated with a spot of coherent light to sense the center position of either the grooves or the land between grooves. The unbalance of the distribution of the reflection of light diffracted from the pre-grooves is used to generate the track position error signal. The track position error signal is fed back to a servo system to control the spot to follow either the center of the grooves or the center of the land between grooves. This method for generating the position error signal is often called the push/pull tracking method.
To increase the storage capability of optical disks, the recorded area on the disk has been expanded to include bi-level optical media. Bi-level optical media is media that has equal land and groove spacing such that data can be recorded on both the lands and the grooves, which allows greater track density on the optical media for a given laser wave length using the push pull tracking method.
With this increased track density, the track pitch becomes narrow relative to the read spot size generated by the laser beam and laser optics. This narrow track pitch leads to significant adjacent track signal interference for both the read only header and read/write user information. There are several possible methods for canceling the adjacent track interference for the read/write user information on the disk. For example bi-level media can be designed to cancel the adjacent track interference of magnetically or reflectivity change marks by adjusting the depth of the groove of the biplanar media. Magnetic super resolution is another method that can be used to mask the adjacent track interference for magnetically recorded marks. However none of these methods helps to cancel the adjacent track interference for the read only header part of the media format because this information is formed by embossed features rather that by magnetic or reflectivity change marks.
Because of this limitation, the master written header for the narrow track pitch bi-level media substrate must be encoded and read in such a way that the sector header information can be reliably read by a single read spot in the presence of significant adjacent track interference.